Individual building blocks are widely spread construction elements, the purchase of such material being most economical. However, the thermal insulating properties thereof remain limited. To improve their thermal properties concrete blocks can be made more lightweight by lightening the concrete. In addition, they can be moulded so as to comprise cells or internal voids to benefit from the insulating properties of air. In this case the cells must be of small size e.g. cells of elongate shape having a thickness of no more than 2 cm. Such blocks are difficult to manufacture however and use a large amount of raw material.
Insulating materials have been arranged inside the cells of blocks of lightweight concrete blocks to improve the heat resistance of these building blocks, thereby forming composite insulating blocks. It is known for example to insert mineral wool, glass wool or polystyrene inside breeze blocks of lightweight concrete. However, the manufacturing process is scarcely economical and/or complex. More recently, it has been proposed to fill the cells with cement foams since cement foams has thermal insulating properties of interest.
However, the filling of cavities contained inside blocks of lightweight concrete with cement foams requires quick-setting foam such as calcium aluminate cement foams. If slow-setting foams is used and inserted in foam form, the foam has a tendency to collapse, to become destabilised and to shrink when hardening and to detach from the cavity walls. Evidently, said phenomenon occurs to the detriment of the thermal properties of such composite blocks.
Quick-setting foams, in particular foams of calcium aluminate cement are economically of little interest and are difficult to use in an industrial process due to the very presence of these quick-setting properties (fouling phenomenon).